Developmental biology is the study of the processes by which organisms grow and develop from a single cell into complex multicellular organisms. This field of biology examines the genetic, molecular, and cellular mechanisms involved in the formation and differentiation of tissues, organs, and organ systems. Researchers in developmental biology investigate how organisms develop through stages such as fertilization, embryogenesis, and morphogenesis. This research area also explores how environmental factors influence development and how abnormalities in development can lead to diseases and birth defects. Overall, developmental biology aims to understand the fundamental processes that govern the formation and organization of complex biological structures in organisms.